In conventional cellular communication networks, a fixed base station (BS) is responsible for controlling communications with the mobile stations (MSs) within the coverage area of that BS. The BS maintains control by selecting channels and communicating directly with the MSs. Thus, conventional cellular communication networks are considered single hop networks.
The limitations of single hop cellular networks are known. For example, the coverage of single hop cellular networks is limited by radio “dead spots” caused by interference from structures (e.g., buildings, etc.) located in the paths of the radiated signals. Also, the coverage of these networks is limited by the transmit power of the MSs. Significant increases in MS transmit power in single hop cellular networks increases signal interference, which decreases network capacity and throughput as a result.
Another limitation of single hop cellular networks is that their channel configurations are fixed. In order to maintain centralized control in single hop cellular networks, the BS selects the channels for communications with the MSs. The channel configuration designs in single hop cellular networks take these centralized control and channel selection features into account. Consequently, the channel configurations of conventional single hop cellular networks are not scalable.
In order to resolve these and other problems encountered with conventional signal hop cellular networks, standards that support multi-hop cellular communications have been approved. For example, IEEE Standard 802.16-2004 (formerly known as IEEE Standard 802.16d) for local and metropolitan area networks specifies the air interface for fixed broadband wireless access (BWA) systems supporting multimedia services. The medium access control (MAC) layer specified in Standard 802.16-2004 supports the use of point-to-multipoint architectures and mesh topologies. Using a mesh topology, a source node in a mesh network can communicate with a destination node via one or more intermediate nodes, and network control is distributed or decentralized. Thus, in the context of a cellular network using a mesh topology, a BS in a multi-hop cellular network can communicate with an MS via one or more fixed or mobile (intermediate) relay stations.
The advantages of multi-hop cellular networks over single hop cellular networks are known. For example, in multi-hop cellular networks, a BS can communicate indirectly with an MS via an intermediate relay station. Consequently, by providing alternate propagation paths, the effects of radio “dead spots” in these networks can be reduced. Also, because intermediate mobile or fixed relay stations can be used in multi-hop cellular networks, the transmit power of the individual MSs in these networks can be reduced. As a result, signal interference in multi-hop cellular networks can be reduced, which increases network capacity and throughput.
Although standards and protocols have been approved that support the use of multi-hop cellular communication networks, a number of important technical problems need to be resolved before such networks can be implemented. For example, in order to implement a multi-hop cellular network successfully, suitable channel configuration and bandwidth allocation mechanisms have to be developed with distributed access and control network objectives in mind.